The present invention is directed to marking materials. More specifically, the present invention is directed to marking materials particularly suitable for use in ballistic aerosol marking apparatus and processes. One embodiment of the present invention is directed to an apparatus for depositing a particulate marking material onto a substrate, comprising (a) a printhead having defined therein at least one channel, each channel having an inner surface and an exit orifice with a width no larger than about 250 microns, the inner surface of each channel having thereon a hydrophobic coating material; (b) a propellant source connected to each channel such that propellant provided by the propellant source can flow through each channel to form propellant streams therein, said propellant streams having kinetic energy, each channel directing the propellant stream through the exit orifice toward the substrate; and (c) a marking material reservoir having an inner surface, said inner surface having thereon the hydrophobic coating material, said reservoir containing particles of a particulate marking material, said reservoir being communicatively connected to each channel such that the particulate marking material from the reservoir can be controllably introduced into the propellant stream in each channel so that the kinetic energy of the propellant stream can cause the particulate marking material to impact the substrate, wherein either (i) the marking material particles of particulate marking material have an outer coating of the hydrophobic coating material; or (ii) the marking material particles have additive particles on the surface thereof, said additive particles having an outer coating of the hydrophobic coating material; or (iii) both the marking material particles and the additive particles have an outer coating of the hydrophobic coating material.
Ink jet is currently a common printing technology. There are a variety of types of ink jet printing, including thermal ink jet printing, piezoelectric ink jet printing, and the like. In ink jet printing processes, liquid ink droplets are ejected from an orifice located at one terminus of a channel. In a thermal ink jet printer, for example, a droplet is ejected by the explosive formation of a vapor bubble within an ink bearing channel. The vapor bubble is formed by means of a heater, in the form of a resistor, located on one surface of the channel.
Several disadvantages can be associated with known ink jet systems. For a 300 spot-per-inch (spi) thermal ink jet system, the exit orifice from which an ink droplet is ejected is typically on the order of about 64 microns in width, with a channel-to-channel spacing (pitch) of typically about 84 microns; for a 600 dpi system, width is typically about 35 microns and pitch is typically about 42 microns. A limit on the size of the exit orifice is imposed by the viscosity of the fluid ink used by these systems. It is possible to lower the viscosity of the ink by diluting it with increasing amounts of liquid (such as water) with an aim to reducing the exit orifice width. The increased liquid content of the ink, however, results in increased wicking, paper wrinkle, and slower drying time of the ejected ink droplet, which negatively affects resolution, image quality (such as minimum spot size, intercolor mixing, spot shape), and the like. The effect of this orifice width limitation is to limit resolution of thermal ink jet printing, for example to well below 900 spi, because spot size is a function of the width of the exit orifice, and resolution is a function of spot size.
Another disadvantage of known ink jet technologies is the difficulty of producing greyscale printing. It is very difficult for an ink jet system to produce varying size spots on a printed substrate. If one lowers the propulsive force (heat in a thermal ink jet system) so as to eject less ink in an attempt to produce a smaller dot, or likewise increases the propulsive force to eject more ink and thereby to produce a larger dot, the trajectory of the ejected droplet is affected. The altered trajectory in turn renders precise dot placement difficult or impossible, and not only makes monochrome greyscale printing problematic, it makes multiple color greyscale ink jet printing impracticable. In addition, preferred greyscale printing is obtained not by varying the dot size, as is the case for thermal ink jet, but by varying the dot density while keeping a constant dot size.
Still another disadvantage of common ink jet systems is rate of marking obtained. Approximately 80 percent of the time required to print a spot is taken by waiting for the ink jet channel to refill with ink by capillary action. To a certain degree, a more dilute ink flows faster, but raises the problem of wicking, substrate wrinkle, drying time, and the like, discussed above.
One problem common to ejection printing systems is that the channels may become clogged. Systems such as thermal ink jet which employ aqueous ink colorants are often sensitive to this problem, and routinely employ non-printing cycles for channel cleaning during operation. This clearing is required, since ink typically sits in an ejector waiting to be ejected during operation, and while sitting may begin to dry and lead to clogging.
Ballistic aerosol marking processes overcome many of these disadvantages. Ballistic aerosol marking is a process for applying a marking material to a substrate, directly or indirectly. In particular, the ballistic aerosol marking system includes a propellant which travels through a channel, and a marking material that is controllably (i.e., modifiable in use) introduced, or metered, into the channel such that energy from the propellant propels the marking material to the substrate. The propellant is usually a dry gas that can continuously flow through the channel while the marking apparatus is in an operative configuration (i.e., in a power-on or similar state ready to mark). Examples of suitable propellants include carbon dioxide gas, nitrogen gas, clean dry ambient air, gaseous products of a chemical reaction, or the like; preferably, non-toxic propellants are employed, although in certain embodiments, such as devices enclosed in a special chamber or the like, a broader range of propellants can be tolerated. The system is referred to as "ballistic aerosol marking" in the sense that marking is achieved by in essence launching a non-colloidal, solid or semi-solid particulate, or alternatively a liquid, marking material at a substrate. The shape of the channel can result in a collimated (or focused) flight of the propellant and marking material onto the substrate.
The propellant can be introduced at a propellant port into the channel to form a propellant stream. A marking material can then be introduced into the propellant stream from one or more marking material inlet ports. The propellant can enter the channel at a high velocity. Alternatively, the propellant can be introduced into the channel at a high pressure, and the channel can include a constriction (for example, de Laval or similar converging/diverging type nozzle) for converting the high pressure of the propellant to high velocity. In such a situation, the propellant is introduced at a port located at a proximal end of the channel (the converging region), and the marking material ports are provided near the distal end of the channel (at or further down-stream of the diverging region), allowing for introduction of marking material into the propellant stream.
In the situation where multiple ports are provided, each port can provide for a different color (for example, cyan, magenta, yellow, and black), pre-marking treatment material (such as a marking material adherent), post-marking treatment material (such as a substrate surface finish material, for example, matte or gloss coating, or the like), marking material not otherwise visible to the unaided eye (for example, magnetic particle-bearing material, ultraviolet-fluorescent material, or the like) or other marking material to be applied to the substrate. Examples of materials suitable for pre-marking treatment and post-marking treatment include polyester resins (either linear or branched); poly(styrenic) homopolymers; poly(acrylate) and poly(methacrylate) homopolymers and mixtures thereof; random copolymers of styrenic monomers with acrylate, methacrylate, or butadiene monomers and mixtures thereof; polyvinyl acetals; poly(vinyl alcohol)s; vinyl alcohol-vinyl acetal copolymers; polycarbonates; mixtures thereof; and the like. The marking material is imparted with kinetic energy from the propellant stream, and ejected from the channel at an exit orifice located at the distal end of the channel in a direction toward a substrate.
One or more such channels can be provided in a structure which, in one embodiment, is referred to herein as a printhead. The width of the exit (or ejection) orifice of a channel is typically on the order of about 250 microns or smaller, and preferably in the range of about 100 microns or smaller. When more than one channel is provided, the pitch, or spacing from edge to edge (or center to center) between adjacent channels can also be on the order of about 250 microns or smaller, and preferably in the range of about 100 microns or smaller. Alternatively, the channels can be staggered, allowing reduced edge-to-edge spacing. The exit orifice and/or some or all of each channel can have a circular, semicircular, oval, square, rectangular, triangular or other cross-sectional shape when viewed along the direction of flow of the propellant stream (the channel's longitudinal axis).
The marking material to be applied to the substrate can be transported to a port by one or more of a wide variety of ways, including simple gravity feed, hydrodynamic, electrostatic, or ultrasonic transport, or the like. The material can be metered out of the port into the propellant stream also by one of a wide variety of ways, including control of the transport mechanism, or a separate system such as pressure balancing, electrostatics, acoustic energy, ink jet, or the like.
The marking material to be applied to the substrate can be a solid or semi-solid particulate material, such as a toner or variety of toners in different colors, a suspension of such a marking material in a carrier, a suspension of such a marking material in a carrier with a charge director, a phase change material, or the like. Preferably the marking material is particulate, solid or semi-solid, and dry or suspended in a liquid carrier. Such a marking material is referred to herein as a particulate marking material. A particulate marking material is to be distinguished from a liquid marking material, dissolved marking material, atomized marking material, or similar non-particulate material, which is generally referred to herein as a liquid marking material. However, ballistic aerosol marking processes are also able to utilize such a liquid marking material in certain applications.
Ballistic aerosol marking processes also enable marking on a wide variety of substrates, including direct marking on non-porous substrates such as polymers, plastics, metals, glass, treated and finished surfaces, and the like. The reduction in wicking and elimination of drying time also provides improved printing to porous substrates such as paper, textiles, ceramics, and the like. In addition, ballistic aerosol marking processes can be configured for indirect marking, such as marking to an intermediate transfer roller or belt, marking to a viscous binder film and nip transfer system, or the like.
The marking material to be deposited on a substrate can be subjected to post ejection modification, such as fusing or drying, overcoating, curing, or the like. In the case of fusing, the kinetic energy of the material to be deposited can itself be sufficient effectively to melt the marking material upon impact with the substrate and fuse it to the substrate. The substrate can be heated to enhance this process. Pressure rollers can be used to cold-fuse the marking material to the substrate. In-flight phase change (solid-liquid-solid) can alternatively be employed. A heated wire in the particle path is one way to accomplish the initial phase change. Alternatively, propellant temperature can accomplish this result. In one embodiment, a laser can be employed to heat and melt the particulate material in-flight to accomplish the initial phase change. The melting and fusing can also be electrostatically assisted (i.e., retaining the particulate material in a desired position to allow ample time for melting and fusing into a final desired position). The type of particulate can also dictate the post-ejection modification. For example, ultraviolet curable materials can be cured by application of ultraviolet radiation, either in flight or when located on the material-bearing substrate.
Since propellant can continuously flow through a channel, channel clogging from the build-up of material is reduced (the propellant effectively continuously cleans the channel). In addition, a closure can be provided that isolates the channels from the environment when the system is not in use. Alternatively, the printhead and substrate support (for example, a platen) can be brought into physical contact to effect a closure of the channel. Initial and terminal cleaning cycles can be designed into operation of the printing system to optimize the cleaning of the channel(s). Waste material cleaned from the system can be deposited in a cleaning station. It is also possible, however, to engage the closure against an orifice to redirect the propellant stream through the port and into the reservoir thereby to flush out the port.
Further details on the ballistic aerosol marking process are disclosed in, for example, Copending Application U.S. Ser. No. 09/163,893, filed Sep. 30, 1998, with the named inventors Gregory B. Anderson, Steven B. Bolte, Dan A. Hays, Warren B. Jackson, Gregory J. Kovacs, Meng H. Lean, Jaan Noolandi, Joel A. Kubby, Eric Peeters, Raj B. Apte, Philip D. Floyd, An-Chang Shi, Frederick J. Endicott, Armin R. Volkel, and Jonathan A. Small, entitled "Ballistic Aerosol Marking Apparatus for Marking a Substrate," Copending Application U.S. Ser. No. 09/164,124, filed Sep. 30, 1998, with the named inventors Gregory B. Anderson, Steven B. Bolte, Dan A. Hays, Warren B. Jackson, Gregory J. Kovacs, Meng H. Lean, Jaan Noolandi, Joel A. Kubby, Eric Peeters, Raj B. Apte, Philip D. Floyd, An-Chang Shi, Frederick J. Endicott, Armin R. Volkel, and Jonathan A. Small, entitled "Method of Marking a Substrate Employing a Ballistic Aerosol Marking Apparatus," Copending Application U.S. Ser. No. 09/164,250 filed Sep. 30, 1998, with the named inventors Gregory B. Anderson, Danielle C. Boils, Steven B. Bolte, Dan A. Hays, Warren B. Jackson, Gregory J. Kovacs, Meng H. Lean, T. Brian McAneney, Maria N. V. McDougall, Karen A. Moffat, Jaan Noolandi, Richard P. N. Veregin, Paul D. Szabo, Joel A. Kubby, Eric Peeters, Raj B. Apte, Philip D. Floyd, An-Chang Shi, Frederick J. Endicott, Armin R. Volkel, and Jonathan A. Small, entitled "Ballistic Aerosol Marking Apparatus for Treating a Substrate," Copending Application U.S. Ser. No. 09/163,808, filed Sep. 30, 1998, with the named inventors Gregory B. Anderson, Danielle C. Boils, Steven B. Bolte, Dan A. Hays, Warren B. Jackson, Gregory J. Kovacs, Meng H. Lean, T. Brian McAneney, Maria N. V. McDougall, Karen A. Moffat, Jaan Noolandi, Richard P. N. Veregin, Paul D. Szabo, Joel A. Kubby, Eric Peeters, Raj B. Apte, Philip D. Floyd, An-Chang Shi, Frederick J. Endicott, Armin R. Volkel, and Jonathan A. Small, entitled "Method of Treating a Substrate Employing a Ballistic Aerosol Marking Apparatus," Copending Application U.S. Ser. No. 09/163,765, filed Sep. 30, 1998, with the named inventors Gregory B. Anderson, Steven B. Bolte, Dan A. Hays, Warren B. Jackson, Gregory J. Kovacs, Meng H. Lean, Joan Noolandi, Joel A. Kubby, Eric Peeters, Raj B. Apte, Philip D. Floyd, An-Chang Shi, Frederick J. Endicott, Armin R. Volkel, and Jonathan A. Small, entitled "Cartridge for Use in a Ballistic Aerosol Marking Apparatus," Copending Application U.S. Ser. No. 09/163,839, filed Sept. 30, 1998, with the named inventors Abdul M. Elhatem, Dan A. Hays, Joan Noolandi, Kaiser H. Wong, Joel A. Kubby, Tuan Anh Vo, and Eric Peeters, entitled "Marking Material Transport," Copending application U.S. Ser. No. 09/163,954, filed Sep. 30, 1998, with the named inventors Gregory B. Anderson, Andrew A. Berlin, Steven B. Bolte, Ga Neville Connell, Dan A. Hays, Warren B. Jackson, Gregory J. Kovacs, Meng H. Lean, Joan Noolandi, Joel A. Kubby, Eric Peeters, Raj B. Apte, Philip D. Floyd, An-Chang Shi, Frederick J. Endicott, Armin R. Volkel, and Jonathan A. Small, entitled "Ballistic Aerosol Marking Apparatus for Marking with a Liquid Material," Copending Application U.S. Ser. No. 09/163,924, filed Sep. 30, 1998, with the named inventors Gregory B. Anderson, Andrew A. Berlin, Steven B. Bolte, Ga Neville Connell, Dan A. Hays, Warren B. Jackson, Gregory J. Kovacs, Meng H. Lean, Joan Noolandi, Joel A. Kubby, Eric Peeters, Raj B. Apte, Philip D. Floyd, An-Chang Shi, Frederick J. Endicott, Armin R. Volkel, and Jonathan A. Small, entitled "Method for Marking with a Liquid Material Using a Ballistic Aerosol Marking Apparatus," Copending Application U.S. Ser. No. 09/163,825, filed Sep. 30, 1998, with the named inventor Kaiser H. Wong, entitled "Multi-Layer Organic Overcoat for Electrode Grid," Copending Application U.S. Ser. No. 09/164,104, filed Sep. 30, 1998, with the named inventors T. Brian McAneney, Jaan Noolandi, and An-Chang Shi, entitled "Kinetic Fusing of a Marking Material," Copending Application U.S. Ser. No. 09/163,904, filed Sep. 30, 1998, with the named inventors Meng H. Lean, Jaan Noolandi, Eric Peeters, Raj B. Apte, Philip D. Floyd, and Armin R. Volkel, entitled "Print Head for Use in a Ballistic Aerosol Marking Apparatus," Copending Application U.S. Ser. No. 09/163,799, filed Sep. 30, 1998, with the named inventors Meng H. Lean, Jaan Noolandi, Eric Peeters, Raj B. Apte, Philip D. Floyd, and Armin R. Volkel, entitled "Method of Making a Print Head for Use in a Ballistic Aerosol Marking Apparatus," Copending Application U.S. Ser. No. 09/163,664, filed Sep. 30, 1998, with the named inventors Bing R. Hsieh, Kaiser H. Wong, and Tuan Anh Vo, entitled "Organic Overcoat for Electrode Grid," and Copending Application U.S. Ser. No. 09/163,518, filed Sep. 30, 1998, with the named inventors Kaiser H. Wong and Tuan Anh Vo, entitled ",Inorganic Overcoat for Particulate Transport Electrode Grid", the disclosures of each of which are totally incorporated herein by reference.
U.S. Pat. No. 5,484,675 (Tripp et al.), the disclosure of which is totally incorporated herein by reference, discloses a toner composition comprising resin and pigment particles, where the pigment particles are treated with a fluorosilane polymer.
U.S. Pat. No. 5,376,172 (Tripp et al.), the disclosure of which is totally incorporated herein by reference, discloses a process for preparing silane treated metal oxides comprising reacting a metal oxide with an amine compound to form an amine metal oxide intermediate, and subsequently reacting said intermediate with a halosilane.
U.S. Pat. No. 5,306,588 (Tanaka et al.), the disclosure of which is totally incorporated herein by reference, discloses a treated silica fine powder and a toner having this powder for use as a toner for developing an electrostatic image. The treated silica fine powder is formed of treated fine silica particles obtained by treating fine silica particles with (a) a first silane coupling agent in which at least one of a substituted secondary alkyl group, an unsubstituted secondary alkyl group, a substituted tertiary alkyl group, an unsubstituted tertiary alkyl group, a substituted cyclic hydrocarbon group, and an unsubstituted cyclic hydrocarbon group is bonded to a silicon atom of the silane coupling agent, and by thereafter treating the resultant fine particles of silica with a second silane coupling agent having the formula EQU (R.sub.1).sub.m --Si--(Y).sub.n
wherein R.sub.1 represents a methyl group, a halomethyl group, a saturated straight chain hydrocarbon group, or an unsaturated straight chain hydrocarbon group, Y represents an alkoxy group or a halogen group, m represents an integer of 1 to 3, n represents an integer of 1 to 3, and the sum of m plus n is 4.
U.S. Pat. No. 5,281,478 (Hohner et al.), the disclosure of which is totally incorporated herein by reference, discloses a method for modifying the surface of finely divided particles, such as pigments and fillers, or of glass fibers. The method utilizes organopolysiloxane with epoxy and long-chain alkyl groups linked over carbon atoms to silicon atoms.
Japanese Patent 2224648, the disclosure of which is totally incorporated herein by reference, discloses a process for preparing metal oxide particles treated with a silicon compound that contains perfluoroalkyl groups.
U.S. Pat. No. 4,960,677 (Seibles et al.), the disclosure of which is totally incorporated herein by reference, discloses a dry nonelectroscopic toner surface coated with 3 to 40 percent by weight of an organofunctional substituted fluorocarbon compound. The toners are useful for developing photosensitive elements having imagewise tacky and complementary nontacky image areas. The surface coating imparts good toning and clean-up characteristics, together with improved performance on aging.
U.S. Pat. No. 4,973,540 (Machida et al.), the disclosure of which is totally incorporated herein by reference, discloses a developer for developing electrostatic latent images formed on an electrostatic latent image carrier, which comprises a toner including a resin, a colorant, and an inorganic fine particle with at least both a negatively chargeable polar group and a positively chargeable polar group on the surface of the inorganic fine particle.
While known compositions and processes are suitable for their intended purposes, a need remains for improved marking processes. In addition, a need remains for improved ballistic aerosol marking processes. Further, a need remains for ballistic aerosol marking processes in which the possibility of the marking material clogging the printing channels is further reduced. Additionally, a need remains for ballistic aerosol marking processes wherein the marking material does not become undesirably charged. There is also a need for ballistic aerosol marking processes wherein the marking material does not adhere to any of the surfaces within the marking device.